The invention is based on a priority application 03291782.5 which is hereby incorporated by reference.
Track clear signalling devices are among the basic devices in railway signalling. These devices ascertain the occupancy status of successive individual sections of a length of track, on the basis of which signalling is carried out to trains entering or passing through this length of track.
Track clear signalling is performed increasingly by means of so-called axle counting systems, in which the axles of trains entering and exiting are counted at individual counting points and these results are compared with one another in a suitable manner. To determine the occupancy of a track section, the axles of a train entering and exiting are counted at certain points at the start of the section by means of a counting-in point and at the end of the section by means of a counting-out point. By forming the difference between the axles counted in and counted out it can be determined whether the track section is clear or occupied, i.e. one of the states “clear” or “occupied” can be assigned to the track section.
In the modern multiple section axle counters from Alcatel SEL AG, for example, the axles are counted in microcontroller-based counting points on the track and the track clear signalling for all track sections is determined in the axle counter evaluation devices in the signal box.
The disadvantage compared with track circuits, in which the track clear signalling is determined by ascertaining the electrical resistance between the rails of a track along the entire track section, is that following a restart of an axle counter it cannot be established initially whether a train is located in the pertinent track section.
Following a restart of an axle counter, a manual reset of the track sections is thus necessary. The reset is relevant to safety and must therefore be carried out with the utmost care. To do this, the following procedures can be executed:
In a first type of reset, the train controller alone assumes full responsibility for carrying this out, once he has satisfied himself visually or by enquiry that the pertinent track section is clear.
In a second type of reset, the train controller likewise assumes responsibility, but to support him a train passes “to order” through the section with caution to ensure that the pertinent track section is clear.
In both the aforementioned types of reset, after it has been ensured that there is no train in the sections under consideration, a manual entry has to be made in the track clear signalling device, with which the pertinent counters or storage devices are then finally reset.
Since the security of the track clear signalling system against malfunctions is indispensable, all faults in the track clear signalling system must be detected and a secure shutdown must ensue as soon as a malfunction is detected. In the case of axle counter evaluation devices with a 2-computer architecture common in safety engineering, this results in a shutdown as soon as one of these computers fails. For routes with a high traffic volume, e.g. main Deutsche Bahn routes, evaluation devices are therefore executed in so-called 2 out of 3 computer technology, in which the failure of one computer can be tolerated and due to which the reliability and availability of the evaluation device and thus of the axle counter system as a whole is markedly increased.
However, in spite of the use of highly reliable computer systems, for example based on the previously mentioned 2 out of 3 computer technology, failures of the system can continue to occur if for example the transmission between one of the counting points and the axle counter evaluation device fails.
A restart of the axle counter system is also always necessary if there is a change in planning data or a software update of the axle counter evaluation device. In all these cases, a time-consuming manual reset that hinders operation continues to be required, as described above.